JP2000214030A - Pressure sensor circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the output of a pressure sensor with stable precision over the entire object environmental temperature range. SOLUTION: The circuit is equipped with the pressure sensor 10 with output temperature characteristics including a primary negative and a secondary downward convex temperature variation component, a temperature sensing circuit 11 for environmental temperature detection which has output temperature characteristics similar to those of the pressure sensor, an amplifying circuit 12 for amplifying the output signal of the pressure sensor 10, am MUX 13 as a switch, and D/A converting circuits 14 and 15. Further, the circuit is equipped with an A/D converting circuit 16 which, while converting the signal from the temperature sensing circuit 11 into a digital signal, converts the signal from the pressure sensor 10 into a digital signal by using the signals from the D/A converting circuits 14 and 15, an EEPROM 17 which stores offset correction quantities and span correction quantities of the pressure sensors 10 by corresponding environmental temperature at specific intervals of the output level of the temperature sensing circuit 11, and a control circuit 18 which reads both correction quantities out of the EEPROM 17 according to the environmental temperature and sends them out to the A/D converting circuit 16 through the D/A converting circuits 14 and 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor circuit having a resistance bridge type pressure sensor and having a highly accurate temperature compensation function.

[0002]

2. Description of the Related Art Conventionally, a pressure sensor circuit having a high-precision temperature compensation function has a memory in which a correction amount for reducing a temperature fluctuation of an output signal of the pressure sensor is stored in advance. In some cases, a correction amount is appropriately read according to the environmental temperature to correct the output signal of the pressure sensor.

FIG. 6 is a configuration diagram of a temperature sensing circuit used in such a conventional pressure sensor circuit, and FIG. 7 is an output temperature characteristic diagram of the temperature sensing circuit shown in FIG.

[0006] A temperature-sensitive circuit 11PA shown in FIG. 6 has a resistance-temperature characteristic in which a resistance value fluctuates greatly with a temperature change, and has a temperature-sensitive resistor R11PA to which a constant voltage is applied to one end, and a resistance value with a temperature change. A resistor R1 having a small variation in resistance-temperature characteristics and connected between the other end of the temperature-sensitive resistor R11PA and the ground.
2PA, temperature-sensitive resistor R11PA and resistor R1
From the connection point of 2PA, a voltage of a level that fluctuates with a change in environmental temperature is output as a result of detection of the environmental temperature, and has a linear negative output temperature characteristic as shown in FIG.

As shown in FIG. 7, a memory in a conventional pressure sensor circuit using such a temperature sensing circuit 11PA includes, for each predetermined interval Δd of the output level of the temperature sensing circuit 11PA,
The correction amount of the pressure sensor for the corresponding environmental temperature is stored. This makes it possible to appropriately read the correction amount from the memory according to the environmental temperature.

JP-A-63-88733 discloses a resistance bridge type pressure sensor, two pairs of temperature sensors having resistances having different temperature characteristics, the pressure sensor and the output of the temperature sensor alternately. A processing circuit for amplifying the supplied outputs of the pressure sensor and the temperature sensor and performing analog / digital exchange to obtain pressure data and temperature data, and a correction circuit for correcting the pressure data obtained by the processing circuit with the temperature data; There is disclosed a pressure detection circuit including:

[0007]

However, in the conventional pressure sensor circuit using the temperature-sensitive circuit having the output temperature characteristic shown in FIG. 7, the output of the pressure sensor over the entire target environmental temperature is stably accurate. There was a problem that could not be corrected.

FIG. 8 is a graph showing an output temperature characteristic of the pressure sensor, and FIG.
Is an output temperature characteristic diagram of the pressure sensor circuit, and the above problem will be described below with reference to this diagram.

When the pressure sensor has an output temperature characteristic including a first-order negative temperature fluctuation component and a second-order downwardly convex temperature fluctuation component as shown in FIG. 8, a predetermined interval of the output level of the temperature-sensitive circuit 11PA. Assuming that the correction amount of the pressure sensor for the corresponding environmental temperature is stored in the memory for each Δd, the correction amounts are stored in the memory at predetermined intervals ΔT of the environmental temperature (see FIG. 7). Such a predetermined interval ΔT
When the output of the pressure sensor having the output temperature characteristic shown in FIG. 8 is corrected by each correction amount, the lower the environmental temperature, the greater the ratio of the output fluctuation of the pressure sensor to the predetermined interval ΔT. The lower the value, the greater the quantization error that occurs between adjacent correction points. As a result, the lower the environmental temperature is, the worse the correction accuracy is. However, the correction point is the intersection of the solid line indicating the output of the pressure sensor and the vertical broken line in FIG.

The present invention has been made in view of the above circumstances, and has as its object to provide a pressure sensor circuit capable of correcting the output of a pressure sensor with stable accuracy over the entire target environmental temperature. .

[0011]

A pressure sensor circuit according to the present invention for solving the above-mentioned problems comprises a pressure sensor which is constituted by a resistor element having a bridge circuit and whose output offset and sensitivity fluctuate with a change in environmental temperature. A temperature sensing circuit for detecting an environmental temperature of the pressure sensor, an amplifier circuit for amplifying an output signal of the pressure sensor, a D / A conversion circuit for correction, and converting a signal from the temperature sensing circuit into a digital signal. On the other hand, an A / D conversion circuit that converts a signal obtained from the pressure sensor into a digital signal through the amplification circuit using a signal from the D / A conversion circuit, and stores a correction amount of the pressure sensor. A correction amount is read out from the memory according to the environmental temperature obtained from the temperature-sensitive circuit via the memory and the A / D conversion circuit, and the A / D conversion circuit is read out via the D / A conversion circuit. And a control circuit for sending to, the temperature sensing circuit is one having an output temperature characteristics similar to the pressure sensor.

In this configuration, for example, when the pressure sensor has an output temperature characteristic including a primary negative temperature fluctuation component and a secondary negative temperature fluctuation component, the output level of the temperature sensing circuit is changed at predetermined intervals. If the correction amounts of the pressure sensors for the corresponding environmental temperatures are stored in the memory in advance, the correction amounts are stored in the memory at smaller temperature intervals as the environmental temperature decreases. When the output temperature characteristic of the pressure sensor via the amplifier circuit is corrected by such a correction amount, the level of a quantization error generated between correction points adjacent to each other becomes constant. This is because the ratio of the output fluctuation of the pressure sensor to the temperature interval between adjacent correction points becomes constant. As a result, the output of the pressure sensor can be corrected with stable accuracy over the entire target environmental temperature.

The pressure sensor has an output temperature characteristic including both primary and secondary temperature fluctuation components, and the memory stores, for each predetermined interval of the output level of the temperature sensing circuit, a corresponding environmental temperature. The correction amount of the pressure sensor described above may be stored. According to this configuration, the output of the pressure sensor can be corrected with stable accuracy over the entire target environmental temperature.

[0014]

FIG. 1 is a schematic configuration diagram of a pressure sensor circuit according to an embodiment of the present invention, and this embodiment will be described below with reference to this drawing.

The present pressure sensor circuit has resistors R101 to R104 in a bridge circuit configuration in which the resistance value changes according to the pressure.
A pressure sensor 10 whose output offset and sensitivity fluctuate with a change in environmental temperature;
A temperature-sensing circuit 11 having the same output temperature characteristic as 0 (specifically, an output temperature characteristic in which the ratio of output fluctuation to a minute temperature interval is substantially the same), and detecting the environmental temperature of the pressure sensor 10;
An amplifier circuit 12 for amplifying an output signal of the pressure sensor 10,
An MUX 13 that performs output switching according to a control signal from a control circuit 18 described later to output one of the outputs of the temperature sensing circuit 11 and the amplification circuit 12, a D / A conversion circuit 14 for offset correction, and a D / A conversion circuit 14 for span correction D / A conversion circuit 15, MUX 13, D / A conversion circuit 14, and D / A
Vin + connected to each output terminal of the conversion circuit 15
It has an input terminal, a Vin-input terminal, and a Vref input terminal, and converts a signal from the temperature sensing circuit 11 into a digital signal, while using both signals from the D / A conversion circuits 14 and 15 to use the amplification circuit 12 and the like. A / D conversion circuit 16 that converts a signal obtained from pressure sensor 10 into a digital signal through
An EEPROM (memory) 17 for storing an offset correction amount and a span correction amount of the pressure sensor 10, and an A / D
The offset correction amount and the span correction amount are read out from the EEPROM 17 in accordance with the environmental temperature obtained from the temperature sensing circuit 11 via the conversion circuit 16, and are read out to the A / D conversion circuit 16 via the D / A conversion circuits 14 and 15, respectively. And a control circuit 18 for transmitting.

However, the pressure sensor 10 detects a physical quantity such as acceleration or pressure as an electrical quantity, and as shown in FIG. 8, a primary negative temperature fluctuation component and a secondary downward temperature fluctuation component. Output temperature characteristics.

When K is a constant, the A / D conversion circuit 16 calculates the D / A conversion circuits 14, 15 as shown in the following equation.
The analog voltage V10 from the pressure sensor 10 is converted into a digital amount D10 by using the analog voltage V14 of the offset correction amount and the analog voltage V15 of the span correction amount obtained respectively from.

D10 = (V10−V14) / V15 × K FIG. 2 is a configuration diagram of a temperature sensing circuit used in the pressure sensor circuit shown in FIG. 1, and FIG. 3 is an output temperature characteristic diagram of the temperature sensing circuit shown in FIG. FIG. 4 is an output temperature characteristic diagram of the pressure sensor obtained through the amplifier circuit in FIG. 1, and FIG. 5 is an output temperature characteristic diagram of the present pressure sensor circuit. , EEPROM 17 and control circuit 18 will be further described.

The temperature-sensitive circuit 11 has a resistance-temperature characteristic in which a resistance value fluctuates greatly with a temperature change, a thermistor R11 to which a constant voltage is applied to one end, and a resistance-temperature characteristic in which a resistance value fluctuates with a temperature change is small. And a resistor R12 connected between the other end of the thermistor R11 and the ground, and detects, from the connection point of the thermistor R11 and the resistor R12, a voltage having a level that fluctuates with a change in the environmental temperature. As a result, as shown in FIG. 3, the output temperature characteristic includes a negative first-order temperature fluctuation component and a second-order downwardly convex temperature fluctuation component.

In the EEPROM 17, the offset correction amount and the span correction amount of the pressure sensor 10 for the corresponding environmental temperature are stored in advance for each predetermined interval Δd of the output level of the temperature sensing circuit 11.

At this time, for each predetermined interval Δd of the output level of the temperature sensing circuit 11, both correction amounts of the pressure sensor for the corresponding environmental temperature are stored in the EEPROM 17 in advance. As shown, the lower the environmental temperature is, the smaller the temperature interval is stored in the EEPROM 17. When the output temperature characteristic shown in FIG. 4 of the pressure sensor 10 via the amplifier circuit 12 is corrected by such a correction amount, as shown in FIG. 5, the level of a quantization error generated between correction points adjacent to each other is obtained. Becomes constant. This is because the ratio of the output fluctuation of the pressure sensor 10 to the temperature interval between the correction points adjacent to each other becomes constant, as in “A” shown in FIG. Thus, the output of the pressure sensor 10 can be corrected with stable accuracy over the entire target environmental temperature. However, the correction point is the intersection of the solid line indicating the output (the output of the substantial pressure sensor 10) in FIG. 4 and the vertical broken line.

Further, the temperature fluctuation component of the offset voltage contained in the signal from the pressure sensor 10 taken into the Vin + input terminal of the A / D conversion circuit 16 is represented by V10 in the above equation.
−Vi, as canceled by the differential of V14
If the output signal of the D / A conversion circuit 14, which is the input signal of the n-input terminal, that is, the value of the offset correction amount for generating this output signal is set and stored in the EEPROM 17, it is included in the analog voltage V10. The temperature fluctuation component of the offset voltage is corrected. V10−V14 after the temperature fluctuation component of the offset voltage is corrected.
, The temperature fluctuation component of the span voltage remains, so that the output of the D / A conversion circuit 15 which becomes an input signal of the Vref input terminal is output so that the temperature fluctuation component of the span voltage is canceled by dividing V10-V14 by V15. Signal, that is, the value of the span correction amount
If it is stored at 17, the temperature fluctuation component of the span voltage will be corrected. However, when the gain of the amplifier circuit 12 with respect to the pressure sensor 10 is G and the output voltage (voltage between a pair of output terminals) of the pressure sensor 10 is V, V × G is the amplification circuit viewed from the A / D conversion circuit 16. 12 is the span voltage of the pressure sensor 10 obtained.

The control circuit 18 is composed of a microcomputer or the like, and performs various controls for each part of the pressure sensor circuit. For example, the control circuit 18 sends a control signal for output switching to the MUX 13.

The control circuit 18 reads the offset correction amount and the span correction amount from the EEPROM 17 using the digital value D11 of the environmental temperature obtained from the temperature sensing circuit 11 via the A / D conversion circuit 16.

Next, the general operation of the pressure sensor circuit will be described. First, the detection result of the temperature sensing circuit 11 is A / D
The digital value D11 is taken into the control circuit 18 via the conversion circuit 16 and the like.

Thereafter, the offset correction amount and the span correction amount corresponding to the digital value D11 are read out from the EEPROM 17, and are respectively read by the D / A conversion circuits 14, 15.
Is sent to the A / D conversion circuit 16 via the. As a result, the digital amount D10 subjected to the offset correction and the span correction is output from the A / D conversion circuit 16 to the outside.

As described above, according to the present embodiment, the output of the pressure sensor 10 can be corrected with stable accuracy over the entire target environmental temperature.

In the present embodiment, the output terminal of the temperature sensing circuit 11 is configured to be directly connected to the input of the MUX 13. However, the present invention is not limited to this.
May be configured to be connected to the input.

[0029]

As is apparent from the above, according to the first aspect of the present invention, there is provided a pressure sensor which is constituted by a resistance element having a bridge circuit and whose output offset and sensitivity fluctuate with a change in environmental temperature. A temperature sensing circuit for detecting an environmental temperature of the pressure sensor, an amplifier circuit for amplifying an output signal of the pressure sensor, a D / A conversion circuit for correction, and converting a signal from the temperature sensing circuit into a digital signal. On the other hand, an A / D conversion circuit that converts a signal obtained from the pressure sensor into a digital signal through the amplification circuit using a signal from the D / A conversion circuit, and stores a correction amount of the pressure sensor. A correction amount is read from the memory in accordance with an environmental temperature obtained from the temperature-sensitive circuit via the memory and the A / D conversion circuit, and the A / D is read via the D / A conversion circuit.
And a control circuit for sending the output signal to the / D conversion circuit. Since the temperature sensing circuit has the same output temperature characteristics as the pressure sensor, the output of the pressure sensor can be output with stable accuracy over the entire target environmental temperature. Correction becomes possible.

According to the second aspect of the present invention, the pressure sensor has an output temperature characteristic including both primary and secondary temperature fluctuation components, and the memory stores the output level of the temperature sensing circuit at a predetermined interval. Each time the correction amount of the pressure sensor for the corresponding environmental temperature is stored, the output of the pressure sensor can be corrected with stable accuracy over the entire target environmental temperature.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a pressure sensor circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a temperature sensing circuit used in the pressure sensor circuit shown in FIG.

FIG. 3 is an output temperature characteristic diagram of the temperature sensing circuit shown in FIG. 2;

FIG. 4 is an output temperature characteristic diagram of the pressure sensor obtained via the amplifier circuit in FIG. 1;

5 is an output temperature characteristic diagram of the pressure sensor circuit shown in FIG.

FIG. 6 is a configuration diagram of a temperature sensing circuit used in a conventional pressure sensor circuit.

7 is an output temperature characteristic diagram of the temperature sensing circuit shown in FIG.

FIG. 8 is an output temperature characteristic diagram of the pressure sensor.

FIG. 9 is an output temperature characteristic diagram of a conventional pressure sensor circuit.

[Explanation of symbols]

 Reference Signs List 10 pressure sensor 11 pressure sensor 12 amplifier circuit 13 MUX 14, 15 D / A conversion circuit 16 A / D conversion circuit 17 EEPROM 18 control circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshio Fujimura 1048 Kazuma Kadoma, Kadoma-shi, Osaka F-term in Matsushita Electric Works, Ltd. (Reference) 2F055 AA40 BB20 CC60 DD20 EE11 FF02 GG32

Claims (2)

[Claims] 1. A pressure sensor comprising a resistance element having a bridge circuit configuration and having an output offset and a sensitivity that fluctuates with a change in environmental temperature, a temperature-sensitive circuit for detecting an environmental temperature of the pressure sensor, and an output of the pressure sensor. An amplifier circuit for amplifying a signal; a D / A conversion circuit for correction; and a signal from the temperature-sensitive circuit, which is converted into a digital signal, and using the signal from the D / A conversion circuit, An A / D conversion circuit for converting a signal obtained from the pressure sensor into a digital signal via a memory, a memory for storing a correction amount of the pressure sensor, and a signal obtained from the temperature sensing circuit via the A / D conversion circuit A control circuit for reading a correction amount from the memory in accordance with the environmental temperature and sending the correction amount to the A / D conversion circuit via the D / A conversion circuit; The pressure sensor circuit having a similar output temperature characteristics. 2. The pressure sensor has an output temperature characteristic including both primary and secondary temperature fluctuation components. The memory stores, for each predetermined interval of an output level of the temperature sensing circuit, a corresponding environmental temperature. 2. The pressure sensor circuit according to claim 1, wherein a correction amount of said pressure sensor is stored.